I am scanning at 200 dpi. Black & White, legal size. For a 100 page scan, I'm getting a file about 40 mb large.
Does this sound write to you? What settings are you using?
Sounds about right. If the sites to which you are scanning have a limit of less (25 mg, etc), I would simply break up the scan into two files. Any less than 200 dpi is not really legible.
Try using OurRecords.com you can upload large files and send documents password protected. The only problem I have found is that sometimes the receiving party needs to check their spam file.
I just converted over to VueScan scanner software and it produces a significant decrease in file size over what my HP scanner software produces. I scanned in a 35 page document at 300 dpi using my standard HP Scanner software and then again using the VueScan. The resulting HP file size was 44.3MB in size and the VueScan was 4.4MB. The HP was set for "high compression" too which certainly isn't doing much. VueScan has drivers for pretty much all the brands of scanners out there whatever you're using. The VueScan standard software is normally $49 but it's on sale right now for $39. I'm loving it so far.
40mb for a 100 page scan sounds good to me